If a national public health institute is releasing an official advisory on a zombie outbreak, shouldn’t we be concerned about the legitimacy of it actually happening? Or is this all one big joke?

The CDC has since updated their website claiming that the zombie guide was a cheeky campaign to engage new audiences.

Yet they maintain their claim that if you have what it takes to survive a zombie apocalypse, you’re more likely to be prepared for a more realistic disaster situation like a hurricane, pandemic or terrorist attack.

Be that as it may, you can’t help but wonder whether or not zombies could be real.

Zombies have their origins in West African and Haitian voodoo, wherein some believe that special sorcerers and spirits have the ability to possess the dead and cause their bodies to rise and walk among the living.

In today’s movies and television, zombies are typically portrayed as victims of some kind of virus or parasite that takes over a person’s body and causes the corpse to become a flesh-eating monster.

Granted, most of these theories have only been tested in fiction, but there is some evidence in nature that zombies could one day be a real threat.

Below we will discuss some of the science and reality behind various forms of potential zombie outbreaks.

Brain Parasites

Some zombies are known to spawn as the result of a parasite infecting and taking over brain function. There are a few known parasites that can cause certain creatures to enter a zombie-like state.

One is called toxoplasmosa gondii and it affects rodents like mice and rats. However, this parasite can only breed in the intestines of cats, so it essentially takes over the rodent’s brain and programs it to find the nearest cat in order to be eaten.

This is kind of a reverse to the typical zombie infection given the (rodent) zombie’s goal is to be eaten, not to eat others.

However, this same parasite is present in nearly half the human population and studies have shown links between it and personality disorders like schizophrenia. After all, one of the reasons scientists use rats in their studies is because their DNA isn’t far off from that of humans.

It may take a while for this particular parasite to evolve to the level where it could breed in the human body, but the potential does theoretically exist.

Neurotoxins

Neurotoxins are chemicals that have the ability to slow your body functions to the point where you could be perceived as dead. Things like lead, ethanol and mercury are forms of poisonous neurotoxins, as is the tetrodotoxin found in puffer and porcupine fish.

Certain drugs and counter-chemicals have been discovered that can bring victims of neurotoxins back to life. Unfortunately, they are reduced to a zombie-like state but can still carry out the basic tasks of eating, sleeping and moving around.

This is the type of practice found in the voodoo culture of Haiti, where there is evidence of this practice being used to pronounce a man dead and bury him only to revive him as a zombie to be put to work in the plantations.

The story is all too real and horrifying, but fortunately there doesn’t appear to be any evidence that these zombies would become aggressive or crave human flesh.

Rage Virus

In some movies, zombies are the victims of some form of supervirus that turns them into enraged killing machines.

Humans can develop certain brain disorders that essentially cause the same thing, but these are individualized cases that are usually the result of serotonin or other chemical imbalances. In these cases the disorders may be the result of genetics, but they have never been contagious.

But then there’s mad cow disease, which attacks a cow’s spinal cord and basically turns it into a zombie cow.

If humans consume the beef from infected cattle, they too can be inflicted with a similar disease that causes very zombie-like symptoms like twitching, discoordination and seizures.

Should this type of virus evolve to the point where it widely affects humans and gets into our food supply, it could plausibly turn us into crazed, mindless zombies out to bite our next victims.

Neurogenesis

Neurogenesis is a relatively modern and innovative science that involves regenerating dead cells, including those in the brain, which were previously thought to be incapable of restoration.

It has already given doctors the ability to restore the brain tissue of comatose trauma patients to the point where they can regain their mobility.

This is a very much unnatural process that causes the brain to slowly die off from the outside in.

Unfortunately, it’s the outside—the cortex—that makes us human. Without it, all we have are basic functions and instincts as a result of the brain stem doing its work.

If, in the process of regenerating, the stem is restored but the cortex dies off, the patient essentially wakes up as an undead zombie.

While this process is potentially quite dangerous, it would take a tremendous undertaking to inflict such damage on a large population of people.

With all of that said, it still remains highly unlikely that a zombie outbreak will occur anytime in the near future—but it could nevertheless happen.

Things like viruses and neurotoxins play an important role in our ecosystems and can be essential for our survival. Most of them have no effect on humans and simply serve to keep nature in balance.

So while you should still follow the advice of the CDC and prepare for a zombie (read: pandemic or natural disaster) apocalypse, the chances of it looking like a zombie horror flick remain quite slim.

Just in case, though, it’s worth learning how to get “zombie fit” so you’re in shape to handle whatever life throws at you (even a severed arm):